General Session: Adult Spinal Deformity - Hall F

Presented by: P. Passias

Author(s):

P. Passias(1), F. Segreto(1), S. Horn(1), C. Bortz(1), D. Vasquez-Montes(1), G. Poorman(1), L. Steinmetz(1), D. Ge(1), P. Zhou(1), B. Diebo(2), J. Moon(1), J. Tishelman(1), A. Sure(1), B. Beaubrun(1), S. Vira(1), C. Jalai(1), J. Buza(1), C. Wang(1), V. Lafage(3), T. Protopsaltis(1), A. Buckland(1), T. Errico(1)

(1) New York University Langone Orthopedic Hospital, Division of Spinal Surgery, New York, NY, United States
(2) SUNY Downstate Medical Center, Department of Orthopaedic Surgery, Brooklyn, NY, United States
(3) Hospital for Special Surgery, Department of Orthopaedic Surgery, New York, NY, United States

Abstract

Introduction: The impact of obesity on lower limb compensation and spinal sagittal alignment is not well understood, especially when considering patients' age-adjusted alignment targets. This study investigates the effect of BMI on age-adjusted alignment targets and lower extremity compensatory mechanisms after adult spinal deformity (ASD) corrective surgery.

Methods: Single-center retrospective review. Inclusion: pts≥18 yrs with full body stereographic x-rays (baseline and 1Y) and met ASD criteria (SVA>5cm, PI-LL>10°, coronal curvature > 20° or pelvic tilt>20°). Patients were stratified into age cohorts: < 40y, 40-65y, ³65y and obesity groups (BMI< 25, 25-30, >30). Correction groups were created at 1Y followup comparing actual alignment with age-adjusted ideal values for Sagittal Vertical Axis (SVA), Pelvic Incidence minus Lumbar Lordosis (PI-LL), Pelvic Tilt and T1 Pelvic Angle (TPA) based on published formulas. Incidence of patients who matched ('M') and unmatched (undercorrected 'U' or overcorrected 'O') ±10 years thresholds for age-adjusted targets was assessed. Health-related quality of life (HRQL) scores, spinal alignment and compensatory mechanisms (knee flexion (KA), hip extension (SFA), ankle flexion (AA), pelvic shift (PS)) were compared across cohorts using ANOVA and paired t-tests.

Results: 116 ASD patients (62yrs, 66% F) were included. Obese patients had less levels fused (6.73) compared to overweight (7.26) and normal (9.79) patients (P< 0.05). PI-LL and TPA significantly improved from baseline to 1Y for all patients (p< 0.05). Obese and overweight patients displayed significantly (P< 0.05) worse SVA (49.83 obese, 52.43 overweight, 26.41 normal), TPA, PI-LL, and pelvic tilt compared to normal weight patients at 1Y (p< 0.05). Obese and overweight patients recruited significantly more pelvic shift (62.36 Obese, 49.80 Overweight, 31.50 Normal) and GSA (6.51 Obese, 6.35 Overweight, 3.40 Normal) at 1Y post-op compared to normal weight patients. Obese patients also displayed no significant postoperative improvement among all 1Y lower-extremity compensation parameters (P>0.05). Obese and overweight patients were less likely to be 'O' for TPA (31% obese, 22.5% overweight, 59.6% normal weight), pelvic tilt (17.2% obese, 17.5% overweight, 38.3% normal), PI-LL (20.7% obese,10.3% overweight, 42.2% normal) and more likely to be 'U' (58.6% obese, 71.8% overweight, 37.8% normal weight) for PI-LL, all P< 0.05. Older overweight patients recruited more ankle flexion, while older normal patients recruited more pelvic shift and GSA at 1Y post-op (P< 0.05). Obese patients of all ages displayed similar (P>0.05) lower extremity compensation outcomes. Obese patients exhibited insignificant postoperative improvements to ODI, EQ5D, VAS Back and Leg, SRS component and total scores (P > 0.05), while overweight and normal patients significantly improved among most HRQL metrics. Obese patients also displayed worse postoperative HRQL outcomes in comparison to overweight and normal patients (P < 0.05).

Conclusion: While all patients benefited from surgery, obese patients were under-corrected and displayed significantly worse alignment and HRQL outcomes compared to normal patients. Obese patients also recruited more postoperative pelvic shift and had greater variation on GSA compared to overweight and normal patients. The benefits from age-adjusted alignment targets appear to be less substantial for obese patients, with obese patients of varying ages exhibiting similar alignment corrections.